Whenever there is a presentation, the audience looks at the 'Presenter' and make a mental gauging/perception of the person ..! Which is not correct but as human beings we all get influenced by what we see first.
A presenter has to be neatly dressed ( nothing flashy or elaborate) and has to have the confident body language which makes the audience look forward to the presentation.
Once the presentation starts, the voice and voice modulation of the presenter plays a big role in the success of the presentation. Many times essence of the presentation is lost just because of the presenter's voice nervous and shaky before a large audience.
This nervousness is the result of the presenter being "nervy " before an audience, the voice sounding different through the speaker system which is not the norm in the day to day communications..!
Hence to overcome this gap, a person should try practising reading LOUDLY ( newspapers, articles etc.) with clear pronunciations, pauses ( where ever necessary) in order for the brain and nervous system to get used to the loud voice..!!
The above point works out very well if practised sincerely..! Good Luck.